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Are the gases coming out when a refrigerator is opened vapours?

Are the gases coming out when a refrigerator is opened vapours? Then why is it called?

Asked by a 7th std student.

Answer:

Air contains humidity (due to the presence of water vapour). Evaporation can take place at any temperature. However the rate of evaporation increases with increase in temperature..

The conversion of a liquid to gas can take place due to evaporation or boiling. but boiling is the phenomenon taking place at a higher but constant temperature.

Due to evaporation (and boiling) the air contains water vapour at room temperature.

When we open the fridge the water vapour condenses to tiny droplets of water and become visible (due to scattering of light).

(I feel that all the concepts might not have been cleared, please ask the questions which arise as comment to this post.)

 

The Physics of Accidents

Accidents

Why are road accident at high speeds very much worse than accidents at low speeds?

Asked Muneem.

Answer:

As you might have studied, greater the speed, greater is the momentum. When an accidents occurs, the greater momentum involved can cause greater damage.

Please ferer to the links below for details

1. http://outreach.phas.ubc.ca/phys420/p420_96/danny/danweb.htm

2. http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/ben_townsend/PhysicsofCarCollisions.htm

 

Rotational Equilibrium – A Numerical Problem

A father and his son are supposed to carry a load of 500 N. They decided to use a uniform pole that is 4.0 m long and weighs 60 N. The father and his son support the pole at the ends. Where should the load be placed so that the father supports three times as much as his son?

Posted by Daniel

Answer:

Let’s represent the situation be the folowing diagram

 

Let the force exerted by son be f

Then the force exerted by father = 3f

Therefore the total force exerted =Total weight = 560N = 4f

Which gives f = 140 N, the force exerted by son

3f=420 N, the force exerted by father

Applying the principle of moments about the point where father holds the rod,

420 x 0 – 500 x x – 60 x 2 + 140 x 4 = 0

==> x = 440/500 = 0.88 m from the end where father holds the load

 

(If there is any problem you find in the solution given, please post as comment to this post.)

Motion of connected system – A numerical problem

What is the acceleration of the body m2 in the diagram below?

(The question was posted by Shuvam Shukla. Students and other visitors can post solution as comments to this post)

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